//
// Created by liyinbin on 2021/4/15.
//
/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// This is version 2 of SpookyHash, incompatible with version 1.
//
// SpookyHash: a 128-bit noncryptographic hash function
// By Bob Jenkins, public domain
//   Oct 31 2010: alpha, framework + SpookyHash::Mix appears right
//   Oct 31 2011: alpha again, Mix only good to 2^^69 but rest appears right
//   Dec 31 2011: beta, improved Mix, tested it for 2-bit deltas
//   Feb  2 2012: production, same bits as beta
//   Feb  5 2012: adjusted definitions of uint* to be more portable
//   Mar 30 2012: 3 bytes/cycle, not 4.  Alpha was 4 but wasn't thorough enough.
//   August 5 2012: SpookyV2 (different results)
//
// Up to 3 bytes/cycle for long messages.  Reasonably fast for short messages.
// All 1 or 2 bit deltas achieve avalanche within 1% bias per output bit.
//
// This was developed for and tested on 64-bit x86-compatible processors.
// It assumes the processor is little-endian.  There is a macro
// controlling whether unaligned reads are allowed (by default they are).
// This should be an equally good hash on big-endian machines, but it will
// compute different results on them than on little-endian machines.
//
// Google's CityHash has similar specs to SpookyHash, and CityHash is faster
// on new Intel boxes.  MD4 and MD5 also have similar specs, but they are orders
// of magnitude slower.  CRCs are two or more times slower, but unlike
// SpookyHash, they have nice math for combining the CRCs of pieces to form
// the CRCs of wholes.  There are also cryptographic hashes, but those are even
// slower than MD5.
//

#ifndef ABEL_HASH_SPOOKY_HASH_V2_H_
#define ABEL_HASH_SPOOKY_HASH_V2_H_


#include <cstddef>
#include <cstdint>

namespace abel {
    namespace hash_internal {

        // clang-format off

        class spooky_hash_v2 {
            static constexpr bool kHasUnalignedAccess = false;
        public:
            //
            // SpookyHash: hash a single message in one call, produce 128-bit output
            //
            static void hash128(
                    const void *message,  // message to hash
                    size_t length,        // length of message in bytes
                    uint64_t *hash1,        // in/out: in seed 1, out hash value 1
                    uint64_t *hash2);       // in/out: in seed 2, out hash value 2

            //
            // Hash64: hash a single message in one call, return 64-bit output
            //
            static uint64_t hash64(
                    const void *message,  // message to hash
                    size_t length,        // length of message in bytes
                    uint64_t seed)          // seed
            {
                uint64_t hash1 = seed;
                hash128(message, length, &hash1, &seed);
                return hash1;
            }

            //
            // Hash32: hash a single message in one call, produce 32-bit output
            //
            static uint32_t hash32(
                    const void *message,  // message to hash
                    size_t length,        // length of message in bytes
                    uint32_t seed)          // seed
            {
                uint64_t hash1 = seed, hash2 = seed;
                hash128(message, length, &hash1, &hash2);
                return (uint32_t) hash1;
            }

            //
            // Init: initialize the context of a SpookyHash
            //
            void init(
                    uint64_t seed1,       // any 64-bit value will do, including 0
                    uint64_t seed2);      // different seeds produce independent hashes

            //
            // Update: add a piece of a message to a SpookyHash state
            //
            void update(
                    const void *message,  // message fragment
                    size_t length);       // length of message fragment in bytes


            //
            // Final: compute the hash for the current SpookyHash state
            //
            // This does not modify the state; you can keep updating it afterward
            //
            // The result is the same as if SpookyHash() had been called with
            // all the pieces concatenated into one message.
            //
            void final(
                    uint64_t *hash1,          // out only: first 64 bits of hash value.
                    uint64_t *hash2) const;   // out only: second 64 bits of hash value.

            //
            // left rotate a 64-bit value by k bytes
            //
            static inline uint64_t Rot64(uint64_t x, int k) {
                return (x << k) | (x >> (64 - k));
            }

            //
            // This is used if the input is 96 bytes long or longer.
            //
            // The internal state is fully overwritten every 96 bytes.
            // Every input bit appears to cause at least 128 bits of entropy
            // before 96 other bytes are combined, when run forward or backward
            //   For every input bit,
            //   Two inputs differing in just that input bit
            //   Where "differ" means xor or subtraction
            //   And the base value is random
            //   When run forward or backwards one Mix
            // I tried 3 pairs of each; they all differed by at least 212 bits.
            //
            static inline void mix(
                    const uint64_t *data,
                    uint64_t &s0, uint64_t &s1, uint64_t &s2, uint64_t &s3,
                    uint64_t &s4, uint64_t &s5, uint64_t &s6, uint64_t &s7,
                    uint64_t &s8, uint64_t &s9, uint64_t &s10, uint64_t &s11) {
                s0 += data[0];
                s2 ^= s10;
                s11 ^= s0;
                s0 = Rot64(s0, 11);
                s11 += s1;
                s1 += data[1];
                s3 ^= s11;
                s0 ^= s1;
                s1 = Rot64(s1, 32);
                s0 += s2;
                s2 += data[2];
                s4 ^= s0;
                s1 ^= s2;
                s2 = Rot64(s2, 43);
                s1 += s3;
                s3 += data[3];
                s5 ^= s1;
                s2 ^= s3;
                s3 = Rot64(s3, 31);
                s2 += s4;
                s4 += data[4];
                s6 ^= s2;
                s3 ^= s4;
                s4 = Rot64(s4, 17);
                s3 += s5;
                s5 += data[5];
                s7 ^= s3;
                s4 ^= s5;
                s5 = Rot64(s5, 28);
                s4 += s6;
                s6 += data[6];
                s8 ^= s4;
                s5 ^= s6;
                s6 = Rot64(s6, 39);
                s5 += s7;
                s7 += data[7];
                s9 ^= s5;
                s6 ^= s7;
                s7 = Rot64(s7, 57);
                s6 += s8;
                s8 += data[8];
                s10 ^= s6;
                s7 ^= s8;
                s8 = Rot64(s8, 55);
                s7 += s9;
                s9 += data[9];
                s11 ^= s7;
                s8 ^= s9;
                s9 = Rot64(s9, 54);
                s8 += s10;
                s10 += data[10];
                s0 ^= s8;
                s9 ^= s10;
                s10 = Rot64(s10, 22);
                s9 += s11;
                s11 += data[11];
                s1 ^= s9;
                s10 ^= s11;
                s11 = Rot64(s11, 46);
                s10 += s0;
            }

            //
            // Mix all 12 inputs together so that h0, h1 are a hash of them all.
            //
            // For two inputs differing in just the input bits
            // Where "differ" means xor or subtraction
            // And the base value is random, or a counting value starting at that bit
            // The final result will have each bit of h0, h1 flip
            // For every input bit,
            // with probability 50 +- .3%
            // For every pair of input bits,
            // with probability 50 +- 3%
            //
            // This does not rely on the last Mix() call having already mixed some.
            // Two iterations was almost good enough for a 64-bit result, but a
            // 128-bit result is reported, so End() does three iterations.
            //
            static inline void end_partial(
                    uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
                    uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
                    uint64_t &h8, uint64_t &h9, uint64_t &h10, uint64_t &h11) {
                h11 += h1;
                h2 ^= h11;
                h1 = Rot64(h1, 44);
                h0 += h2;
                h3 ^= h0;
                h2 = Rot64(h2, 15);
                h1 += h3;
                h4 ^= h1;
                h3 = Rot64(h3, 34);
                h2 += h4;
                h5 ^= h2;
                h4 = Rot64(h4, 21);
                h3 += h5;
                h6 ^= h3;
                h5 = Rot64(h5, 38);
                h4 += h6;
                h7 ^= h4;
                h6 = Rot64(h6, 33);
                h5 += h7;
                h8 ^= h5;
                h7 = Rot64(h7, 10);
                h6 += h8;
                h9 ^= h6;
                h8 = Rot64(h8, 13);
                h7 += h9;
                h10 ^= h7;
                h9 = Rot64(h9, 38);
                h8 += h10;
                h11 ^= h8;
                h10 = Rot64(h10, 53);
                h9 += h11;
                h0 ^= h9;
                h11 = Rot64(h11, 42);
                h10 += h0;
                h1 ^= h10;
                h0 = Rot64(h0, 54);
            }

            static inline void end(
                    const uint64_t *data,
                    uint64_t &h0, uint64_t &h1, uint64_t &h2, uint64_t &h3,
                    uint64_t &h4, uint64_t &h5, uint64_t &h6, uint64_t &h7,
                    uint64_t &h8, uint64_t &h9, uint64_t &h10, uint64_t &h11) {
                h0 += data[0];
                h1 += data[1];
                h2 += data[2];
                h3 += data[3];
                h4 += data[4];
                h5 += data[5];
                h6 += data[6];
                h7 += data[7];
                h8 += data[8];
                h9 += data[9];
                h10 += data[10];
                h11 += data[11];
                end_partial(h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
                end_partial(h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
                end_partial(h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11);
            }

            //
            // The goal is for each bit of the input to expand into 128 bits of
            //   apparent entropy before it is fully overwritten.
            // n trials both set and cleared at least m bits of h0 h1 h2 h3
            //   n: 2   m: 29
            //   n: 3   m: 46
            //   n: 4   m: 57
            //   n: 5   m: 107
            //   n: 6   m: 146
            //   n: 7   m: 152
            // when run forwards or backwards
            // for all 1-bit and 2-bit diffs
            // with diffs defined by either xor or subtraction
            // with a base of all zeros plus a counter, or plus another bit, or random
            //
            static inline void short_mix(uint64_t &h0, uint64_t &h1,
                                        uint64_t &h2, uint64_t &h3) {
                h2 = Rot64(h2, 50);
                h2 += h3;
                h0 ^= h2;
                h3 = Rot64(h3, 52);
                h3 += h0;
                h1 ^= h3;
                h0 = Rot64(h0, 30);
                h0 += h1;
                h2 ^= h0;
                h1 = Rot64(h1, 41);
                h1 += h2;
                h3 ^= h1;
                h2 = Rot64(h2, 54);
                h2 += h3;
                h0 ^= h2;
                h3 = Rot64(h3, 48);
                h3 += h0;
                h1 ^= h3;
                h0 = Rot64(h0, 38);
                h0 += h1;
                h2 ^= h0;
                h1 = Rot64(h1, 37);
                h1 += h2;
                h3 ^= h1;
                h2 = Rot64(h2, 62);
                h2 += h3;
                h0 ^= h2;
                h3 = Rot64(h3, 34);
                h3 += h0;
                h1 ^= h3;
                h0 = Rot64(h0, 5);
                h0 += h1;
                h2 ^= h0;
                h1 = Rot64(h1, 36);
                h1 += h2;
                h3 ^= h1;
            }

            //
            // Mix all 4 inputs together so that h0, h1 are a hash of them all.
            //
            // For two inputs differing in just the input bits
            // Where "differ" means xor or subtraction
            // And the base value is random, or a counting value starting at that bit
            // The final result will have each bit of h0, h1 flip
            // For every input bit,
            // with probability 50 +- .3% (it is probably better than that)
            // For every pair of input bits,
            // with probability 50 +- .75% (the worst case is approximately that)
            //
            static inline void short_end(uint64_t &h0, uint64_t &h1,
                                        uint64_t &h2, uint64_t &h3) {
                h3 ^= h2;
                h2 = Rot64(h2, 15);
                h3 += h2;
                h0 ^= h3;
                h3 = Rot64(h3, 52);
                h0 += h3;
                h1 ^= h0;
                h0 = Rot64(h0, 26);
                h1 += h0;
                h2 ^= h1;
                h1 = Rot64(h1, 51);
                h2 += h1;
                h3 ^= h2;
                h2 = Rot64(h2, 28);
                h3 += h2;
                h0 ^= h3;
                h3 = Rot64(h3, 9);
                h0 += h3;
                h1 ^= h0;
                h0 = Rot64(h0, 47);
                h1 += h0;
                h2 ^= h1;
                h1 = Rot64(h1, 54);
                h2 += h1;
                h3 ^= h2;
                h2 = Rot64(h2, 32);
                h3 += h2;
                h0 ^= h3;
                h3 = Rot64(h3, 25);
                h0 += h3;
                h1 ^= h0;
                h0 = Rot64(h0, 63);
                h1 += h0;
            }

        private:

            //
            // short_hash is used for messages under 192 bytes in length
            // short_hash has a low startup cost, the normal mode is good for long
            // keys, the cost crossover is at about 192 bytes.  The two modes were
            // held to the same quality bar.
            //
            static void short_hash(
                    const void *message,  // message (byte array, not necessarily aligned)
                    size_t length,        // length of message (in bytes)
                    uint64_t *hash1,        // in/out: in the seed, out the hash value
                    uint64_t *hash2);       // in/out: in the seed, out the hash value

            // number of uint64_t's in internal state
            static constexpr size_t sc_numVars = 12;

            // size of the internal state
            static constexpr size_t sc_blockSize = sc_numVars * 8;

            // size of buffer of unhashed data, in bytes
            static constexpr size_t sc_bufSize = 2 * sc_blockSize;

            //
            // sc_const: a constant which:
            //  * is not zero
            //  * is odd
            //  * is a not-very-regular mix of 1's and 0's
            //  * does not need any other special mathematical properties
            //
            static constexpr uint64_t sc_const = 0xdeadbeefdeadbeefULL;

            uint64_t m_data[2 * sc_numVars];   // unhashed data, for partial messages
            uint64_t m_state[sc_numVars];  // internal state of the hash
            size_t m_length;             // total length of the input so far
            uint8_t m_remainder;          // length of unhashed data stashed in m_data
        };

        // clang-format on

    } // namespace hash_internal
} // namespace abel
#endif  // ABEL_HASH_SPOOKY_HASH_V2_H_
